This invention relates generally to a protective cover for containers and in particular, it relates to a cover adapted to be used in connection with an aluminum pan containing raw corn kernels and oil covered by a thin aluminum foil folded or wrinkled in such a manner as to expand during heating of the container and its contents in order to accomodate the expanded volume of the popped corn. The aluminum foil used in such an expandable cover is of extremely thin gauge considerably thinner than the aluminum used for the bottom and sides of the pan. Owing to its thinness the aluminum foil in the cover is susceptible to damage or perforation. It is therefore necessary to employ an additional protective cover over the top of the expansible aluminum foil when it is offered for sale and the cover must be easily removable. Generally, a paperboard cover is used and, in addition to serving the protective function, it also permits display of advertising matter and identification of the product as well as directions for use. The paperboard cover is marginally anchored on the container by the crimping margin of the aluminum foil of both the expansible top and the relatively thick container sides.
Prior to heating the popped corn package, a major central part of the paperboard cover must be removed in order to permit the expansible aluminum top to expand through a remaining annular portion of the paperboard cover during the heating. This annular portion of the paperboard cover acts as a gasket for the pan and the thin expansible foil to reduce the loss of steam during popping thus causing the package to function successfully.
To facilitate the removal of the cover, one or more cut scores extend on both surfaces of the cover around the peripheral portion thereof. The depth of the cut scores is usually less than the depth of the paperboard cover. In order to define a finger tab there has been provided an angular cut terminating in the outer peripheral cut score. When the finger tab is gripped and pulled, the paperboard cover is thrown away along the cut score lines thereby exposing the expansible aluminum foil top and leaving, around the rim of the container a narrow marginal band of paperboard.
A paperboard container cover that is scored and cut so as to facilitate easy removal of a major portion thereof, as described hereinabove, is disclosed in U.S. Pat. Nos. 3,054,680 and 3,110,233.
Openable paperboard covers disclosed in the above patents have been used for several years in connection with the pop corn producing containers. The angular cut shape defining a finger tab which acts as a starter for the lid opening and removal of the same has been used because it helps minimize moisture vapor transmission and helps prevent accidental puncturing of the spun aluminum located underneath. Prior to using the angular cut shape, other die cut shapes were used, however, these proved faulty for one reason or another.
Nonetheless due to the fact that the angular pull tab is normally in the plane of the upper surface of the lip, it has been necessary first to lift the sides of the angular cut. The delicate spun aluminum foil has been frequently punctured by a fingernail or other object when the lid opening process has been started. A small protective circular top has been placed underneath the area of the angular cut but despite this precaution the above-mentioned problem has still taken place.
It is therefore a primary object of this invention to provide a paperboard cover for prepackaged foods container which eliminates the danger of puncturing the underlying aluminum foil of the container.
Another object of this invention is to improve existing cover with minimum structural changes.